Diversity among lactococci isolated from ewes' raw milk and cheese

Area of Science:

• Food Microbiology
• Dairy Science
• Bacteriology

Background:

• Lactococci are key lactic acid bacteria (LAB) in raw milk fermentations.
• Understanding their technological and genetic traits is crucial for cheese production.

Purpose of the Study:

• Investigate the seasonal variations in technological and genetic characteristics of lactococci in ewes' raw milk and cheese.
• Identify fast acid-producing lactococci and their genetic diversity.

Main Methods:

• Isolation and characterization of LAB from ewes' raw milk and cheese over a year.
• Assessing acid production capacity (pH decrease).
• Identification of Lactococcus species using polymerase chain reaction (PCR) and genetic diversity analysis via randomly amplified polymorphic DNA (RAPD) fingerprinting.

Main Results:

• Fast acid-producing LAB proportions varied seasonally, peaking in spring for both milk and cheese.
• Lactococcus lactis subspecies (lactis, cremoris, and lactis biovar diacetylactis) were the primary fast acid producers.
• RAPD fingerprinting revealed significant genetic diversity within L. lactis subspecies, with up to 21 patterns for L. lactis subsp. lactis.

Conclusions:

• Seasonal factors significantly influence the acid production capacity of lactococci in ewe's milk and cheese.
• Lactococcus lactis exhibits substantial genetic diversity, impacting its technological properties in dairy fermentations.
• This genetic variability is important for starter culture development and cheese quality.